1. Field of the Invention
The invention relates generally to chemical material removal processes and more particularly to removal of excess etchant from the workpiece in a chemical material removal process.
2. Description of the Prior Art
Chemical material removal processes, which use chemicals as "cutting tools," involve the use of acid and alkaline solutions to etch away unwanted material, leaving the final desired pattern or part. An acid or alkaline resistant material (known as a maskant or a resist) is applied to certain portions of the workpiece, and subsequent application of an etchant removes the desired material, leaving unaffected the material covered by the resist. The etchant is applied to the workpiece in an etching chamber by immersion, splash, or spray. Following etching, the workpiece is generally washed to remove excess etchant.
In the prior art, disposal of the excess etchant has been costly, especially where a high density etchant is used, and sometimes has precluded the use of an etchant that is otherwise chemically and metallurgically acceptable. The excess etchant is neutralized to a pH of approximately nine and then pumped to a settling tank. Generally the etchant has a higher density than water and will settle to the bottom of the tank along with any other impurities. The sludge from the bottom of the settling tank is pumped out and transported to a waste disposal area. The solution which flows from the top of the tank contains fewer impurities and is therefore sent directly to the sewer system. The particle content of waste introduced into sewer lines must meet strict standards. Where a plant produces large quantities of waste etchant, compliance with these standards is difficult and expensive.
Chemcut Corporation, a manufacturer of etching systems, uses a blower installed adjacent to the etching chamber and below the workpiece travel path for blowing air directed at the workpiece to remove some excess etchant. However, this system has proved to be inadequate for reducing waste etchant. The blower used by Chemcut has only been effective in removing approximately ten percent of the excess etchant. A further disadvantage is that the blower always remains on, whether or not a workpiece is present.